NERVOUS SYSTEM OF A TWO-HEADED PIG EMBRYO 



403 



V. Nervus trigeminus. The fifth nerve arises in typical 

 normal manner by a large sensory and a small motor root from 

 the ventrolateral surface of the pons, just at the pontine flexure. 

 Immediately outside of the dura mater the sensory root expands 

 into the large gasserian ganglion, which gives rise to the oph- 

 thalmic, maxillary, and mandibular divisions characteristic of the 

 fifth nerve (fig.. 4), Not all of the secondary branches of these 



Fig. 16 Section through the internal ear labj^rinth of the outer (normal) 

 sides of the embryo, the sphenopalatine ganglia of the outer sides, and the 

 median (conjoined) periotic cartilages. S. 262. 



are as yet developed, and only those that have definite relation 

 to the median region are labeled in the figures. 



Almost from its beginning the motor root is embedded in the 

 gasserian ganglion, and ultimately becomes merged with the 

 mandibular branch (figs. 13 to 15). 



The ophthalmic division courses rostralward over the optic 

 nerve and beneath the trochlear, and divides into normal ter- 

 minal branches. The nasal and infratrochlear branches are 

 readily traced to their terminations. 



